JP7425958B2 - Compositions for thick film resistors, pastes for thick film resistors, and thick film resistors - Google Patents

Description

The present invention relates to a composition for a thick film resistor and a paste for a thick film resistor used in the manufacture of electronic components such as chip resistors, hybrid ICs, or resistor networks. Furthermore, the present invention relates to a thick film resistor formed using a thick film resistor paste.

Generally, thick film resistors such as chip resistors, hybrid ICs, or resistor networks are formed by printing and firing a resistor paste on a ceramic substrate.
Among such thick film resistors, thick film resistors with a sheet resistance value of 30Ω or less have a composition for the thick film resistor containing conductive powder such as Ag powder or Pd powder and glass powder as main components. are widely used.

The reason why these Ag powder, Pd powder, and glass powder are used for thick film resistors is that they can be fired in air and have a temperature coefficient of resistance (TCR) close to 0, as well as being 30Ω or less. For example, it is possible to form a resistor with a resistance value in the range of .

Here, the temperature coefficient of resistance (TCR) is determined as follows.
The resistance temperature coefficient is determined by measuring the resistance value of the thick film resistor after holding it at -55°C, 25°C, and 125°C, respectively, and calculating the resistance value of each thick film resistor at each temperature as R _-55 and R ₂₅ , R ₁₂₅ , various resistance temperature coefficients are determined using the following equations (1) and (2).

The temperature coefficient of resistance (TCR) of a resistor made of Ag powder, Pd powder, and glass powder changes depending on the blending ratio of Ag and Pd, and the temperature coefficient of resistance is the lowest when Ag is approximately 44% by mass and Pd is approximately 56% by mass. is closest to 0, and as the mass ratio deviates from this mass ratio, the temperature coefficient of resistance increases in a positive direction. Patent Document 1 utilizes this fact to propose a resistor composition whose temperature coefficient of resistance is close to zero.

However, a resistor formed from Ag powder, Pd powder, and glass powder has a drawback that the temperature coefficient of resistance (TCR) varies depending on the distance between the electrodes.
A resistor with such a thick film resistor is made by pasting a thick film resistor composition consisting of Ag powder, Pd powder, and glass powder so as to straddle opposing electrodes whose main component is Ag. When a paste for a film resistor is printed and fired, the Ag in the electrode diffuses into the thick film resistor during the firing process of the paste for a thick film resistor, changing the ratio of Ag and Pd set in the resistor. It's going to happen.
For this reason, in a small-sized resistor, the distance between the electrodes becomes narrow, and the amount of Ag that diffuses from the electrode material into the resistor increases, resulting in a problem that the temperature coefficient of resistance (TCR) becomes higher than that in a large-sized resistor. In other words, the temperature coefficient of resistance (TCR) changes depending on the size of resistors having approximately the same resistance value, which reduces the degree of freedom in circuit design.

Patent No. 2986539

The object of the present invention is to provide a composition for a thick film resistor, a paste for a thick film resistor, and a paste for a thick film resistor, which are made of Ag powder, Pd powder, and glass powder, and whose temperature coefficient of resistance (TCR) fluctuates little even when the distance between electrodes changes. An object of the present invention is to provide a membrane resistor.

A first aspect of the present invention includes a noble metal powder, a glass powder that does not substantially contain lead, and amorphous silica with a particle size of 50 nm or less, and the noble metal powder includes 40 to 80% by mass of Ag powder. , a mixed powder consisting of Pd powder with the remainder being Pd powder, or an alloy powder containing 40 to 80% by mass of Ag and consisting of Pd and unavoidable impurities; The composition for a thick film resistor is characterized in that the glass powder is contained in an amount of 1 to 100 parts by weight and the amorphous silica is contained in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the noble metal powder.

A second invention of the present invention is a composition for a thick film resistor, characterized in that the glass powder in the first invention has a particle size distribution D ₅₀ of 0.5 μm to 5 μm.

A third invention of the present invention is a paste for a thick film resistor comprising the composition for a thick film resistor according to the first or second invention and an organic vehicle in which a resin is dissolved in a solvent .

A fourth aspect of the present invention is a thick film resistor comprising a noble metal, glass substantially free of lead, and amorphous silica with a particle size of 50 nm or less, wherein the thick film resistor is a fired body. , the noble metal contains 40 to 80% by mass of Ag, and the balance consists of Pd and unavoidable impurities, and the glass has a softening point of 650° C. or more and 850° C. or less, and the glass is added to 100 parts by mass of the noble metal. 1 to 100 parts by mass of the amorphous silica, and 0.5 to 20 parts by mass of the amorphous silica.

The present invention solves the problem of a composition for a thick film resistor containing amorphous silica with a particle size of 50 nm or less in a composition for a thick film resistor mainly composed of glass powder not containing Ag, Pd, and lead. According to the present invention, a composition for a thick film resistor and a thick film whose temperature coefficient of resistance (TCR) changes little even if the distance between the electrodes of electrodes containing Ag as a main component are changed. It is now possible to provide pastes for resistors, and by using them, it is possible to provide thick film resistors with small fluctuations in temperature coefficient of resistance.

The present invention utilizes the fact that amorphous silica with a particle size of 50 nm or less inhibits the diffusion of Ag in the electrode into the resistor during the firing process of a composition for a thick film resistor. According to the present invention, it is possible to provide a thick film resistor with a small difference in temperature coefficient of resistance even when the same composition for a thick film resistor is used to obtain thick film resistors having different distances between electrodes, which has been difficult in the past.
To explain in more detail, the composition for a thick film resistor according to the present invention is fired at a peak temperature of 800° C. to 900° C. to form a thick film resistor. This thick film resistor is made by applying a paste for thick film resistors made of a composition for thick film resistors to a ceramic substrate such as alumina, on which thick film electrodes containing Ag as a main component are placed facing each other. It is formed by printing across these electrodes and firing. The composition for a thick film resistor according to the present invention utilizes the fact that the amorphous silica contained inhibits the diffusion of Ag in the electrode into the resistor.

The composition for a thick film resistor of the present invention contains Ag and Pd as noble metal powder.
The ratio of both contents (content in mass %) is Ag:Pd=40:60 to 80:20. If the ratio is other than this, the temperature coefficient of resistance (TCR) of the resistor may exceed 1000 and become too large on the plus side.
Therefore, in order to make the temperature coefficient of resistance (TCR) close to 0, it is desirable that the ratio/Ag:Pd=40:60 to 45:55. That is, a mixed powder of 40% by mass of Ag powder and the balance of Pd powder, or an alloy powder containing 40% by mass of Ag and the balance of Pd and unavoidable impurities is desirable.

According to the present invention, when Ag:Pd=44:56, the temperature coefficient of resistance (TCR) can be made within 100 ppm/°C. Further, when mixed at a ratio of Ag:Pd=70:30, the resulting temperature coefficient of resistance (TCR) is about 400 ppm/°C, and can be within 500 ppm/°C.
In the present invention, Ag and Pd may exist in a mixed powder of Ag powder and Pd powder, or may be an alloy powder, and the particle size thereof is preferably 0.1 μm to 5.0 μm.

The glass powder contained in the present invention preferably does not contain lead, has a softening point of 650° C. or higher and 900° C. or lower, and has a particle size distribution of _D50 of 0.5 μm to 5.0 μm. More preferably, the softening point is 650°C or higher and 850°C or lower.
If the softening point of this glass powder is lower than 650°C, PdO produced by oxidation of Pd will remain during the firing process of the thick film resistor composition of the present invention, and the ratio of Ag and Pd in the noble metals will change, resulting in a decrease in resistance value. The temperature coefficient of resistance becomes high. If the softening point of the glass powder is 650° C. or higher, PdO generated during the firing process is reduced and forms an Ag--Pd alloy with Ag, so that the temperature coefficient of resistance of the resistor does not become too high. On the other hand, the softening point is desirably 900°C or lower; if it exceeds 900°C, it becomes difficult to sinter the thick film resistor composition at a peak temperature of 800°C to 900°C.

Furthermore, if the particle size of the glass powder is smaller than 0.5 μm, the glass powder will soften excessively at low temperatures, making it difficult to reduce PdO generated during the firing process. On the other hand, if the particle size of the glass powder is larger than 5.0 μm, the variation in the resistance value of the thick film resistor becomes large.

By the way, the composition of the glass powder is not limited, but an aluminoborosilicate composition containing an oxide of an alkaline earth metal is suitable. Moreover, Zn, an alkali metal element, etc. can be appropriately added to the composition of the glass powder.
Note that the softening point of the glass powder is defined as a temperature higher than the temperature at which a decrease in the differential thermal curve on the lowest temperature side of the differential thermal curve obtained by the differential thermal analysis (TG-DTA) of the glass powder appears. The next differential thermal curve is the decreasing peak temperature.
The particle size _D50 of the glass powder is the median value of the volume distribution diameter measured by a laser diffraction scattering type particle size distribution analyzer.

Amorphous silica having a particle size of 50 nm or less is essential to the composition for a thick film resistor of the present invention.
This amorphous silica with a particle size of 50 nm or less surrounds the noble metal powder and glass powder, suppresses the diffusion of Ag from the electrode during the firing process, and delays the softening of the glass powder, but it softens as it approaches the peak temperature. It will melt into the glass. As a result, even if the distance between the electrodes is small, the diffusion of Ag from the electrodes is small, the ratio of Ag and Pd in the thick film resistor becomes close to the designed value, and the temperature coefficient of resistance of the thick film resistor approaches 0. I can do it.
If the particle size of the amorphous silica is larger than 50 nm, it will not be possible to cover the surroundings of the noble metal powder and glass powder, and the diffusion of Ag from the electrode will not be suppressed.

In the present invention, it is necessary that the glass powder be 1 to 100 parts by mass and the amorphous silica be 0.5 to 20 parts by mass relative to 100 parts by mass of the noble metal powder. If the amount of glass powder is less than 1 part by mass, the adhesion strength of the thick film resistor will be significantly weakened. Moreover, if the amount of glass powder is more than 100 parts by mass, the variation in the resistance value of the resistor becomes too large. When the amount of amorphous silica is less than 0.5 parts by mass, it becomes impossible to suppress the diffusion of Ag from the electrodes, and the temperature coefficient of resistance (TCR) of the thick film resistor with a small distance between the electrodes becomes high. Moreover, if the amount of amorphous silica is more than 20 parts by mass, the silica will not fully dissolve into the glass, and the variation in the resistance value of the thick film resistor will become too large.

Additives commonly used for the purpose of improving or adjusting the resistance value, temperature coefficient of resistance, load characteristics, and trimming properties of thick film resistors may be added to the composition for thick film resistors of the present invention. Typical additives include Nb ₂ O ₅ , Ta ₂ O ₅ , TiO ₂ , CuO, MnO ₂ , ZrO ₂ , Al ₂ O ₃ , ZrSiO ₄ and the like. The amount added is adjusted depending on the purpose, but is usually 20 parts by mass or less per 100 parts by mass of the noble metal powder and glass powder.

The composition for a thick film resistor of the present invention is mixed and dispersed in an organic vehicle together with additives as necessary to form a paste for a thick film resistor for printing. The organic vehicle is not particularly limited, and a solution of a resin such as ethyl cellulose, acrylic ester, methacrylic ester, rosin, or maleic ester dissolved in a solvent such as terpineol, butyl carbitol, or butyl carbitol acetate is used. Further, a dispersant, a plasticizer, etc. can be added as necessary. Although the dispersion method is not particularly limited, it is common to use a three-roll mill, a bead mill, a planetary mill, etc. for dispersing fine particles. The blending ratio of the organic vehicle is appropriately adjusted depending on the printing or coating method, but it is 20 to 200 parts by mass based on 100 parts by mass of the noble metal powder, glass powder, and amorphous silica.

Thick film resistors are made by applying a paste for thick film resistors made of a composition for thick film resistors to a substrate made of ceramics such as alumina, with thick film electrodes containing Ag as a main component facing each other. It can be manufactured by printing across the electrodes and firing. A glass paste or the like can be applied to the surface of the thick film resistor and fired at a temperature of about 600° C., which is lower than the temperature at which the thick film resistor was fired, to form a glass coating film or the like.

Although the present invention will be specifically explained, the present invention is not limited to these Examples.
In the examples and comparative examples of the present invention, Ag powder with a particle size of 1.0 μm, Pd powder with a particle size of 0.5 μm, glass powder A with a particle size D ₅₀ of 1.3 μm and a softening point of 650° C., and a particle size D ₅₀ of 1.4 μm A resistance paste was prepared by using glass powder B having a softening point of 560° C. and amorphous silica having a particle size of 45 nm and dispersing it in an organic vehicle using a three-roll mill according to the paste formulation shown in Table 2.
Details of glass powder A and glass powder B are shown in Table 1.
Further, an organic vehicle was prepared by mixing ethyl cellulose and terpineol at a mass ratio of 15:85.

Next, the prepared resistance paste was printed on an electrode of 1 mass % Pd and 99 mass % Ag that had been previously formed by firing on an alumina substrate, and after drying at 150°C for 5 minutes, the paste was dried at a peak temperature of 850°C. A thick film resistor was formed by firing for 9 minutes, a total of 30 minutes.
The size of the thick film resistor is one in which the resistor width is 0.5 mm and the resistor length (between electrodes) is 50 mm, and the other is 1 mm in resistor width and 1 mm in resistor length (between electrodes). There are two ways to do this.

The formed thick film resistor has a film thickness, a sheet resistance value, a temperature coefficient of resistance (COLD-TCR) from 25°C to -55°C, and a temperature coefficient of resistance (COLD-TCR) from 25°C to 125°C. HOT-TCR) was measured.
The film thickness was determined by averaging the film thicknesses of five thick film resistors measured using a stylus thickness roughness meter.
The resistance value was determined by averaging the resistance values of 25 thick film resistors each having a resistor width of 1 mm and a resistor length (between electrodes) of 1 mm using a digital multimeter.

Temperature coefficient of resistance (TCR) is determined by holding the thick film resistor at -55°C, 25°C, and ₁₂₅ °C for 15 minutes _and then measuring the resistance value _. It was calculated using the following equations (3) and (4), and the average of five thick film resistors was taken. It is desirable that the temperature coefficient of resistance is close to zero.

In Example 1, a mixed noble metal powder in which Ag powder and Pd powder were mixed at a mass ratio of 70:30 was used to prepare a paste with the paste composition shown in Table 2, and was fired to produce a thick film resistor. The body was created.
Table 3 shows the above measurement results of the produced thick film resistor.

(Comparative example 1)
A thick film resistor was produced under the same conditions as in Example 1, except that the paste did not contain silica powder. Table 2 shows the paste formulation, and Table 3 shows the measurement results.

In Example 2, a mixed noble metal powder in which Ag powder and Pd powder were mixed at a mass ratio of 44:56 was used to prepare a paste with the paste composition shown in Table 4, and baked it to produce a thick film resistor. The body was created.
Table 5 shows the above measurement results of the produced thick film resistor.

In Example 3, a mixed noble metal powder in which Ag powder and Pd powder were mixed at a mass ratio of 44:56 was used, and a paste was prepared according to the paste composition shown in Table 4 and fired to produce a thick film resistor. did.
Table 5 shows the measurement results of the thick film resistor.

(Comparative example 2)
A thick film resistor was produced under the same conditions as in Example 2, except that the paste did not contain silica powder. Table 4 shows the paste formulation, and Table 5 shows the measurement results.

(Comparative example 3)
A thick film resistor was produced under the same conditions as in Example 2, except that glass powder B was used instead of glass powder A. Table 4 shows the paste formulation, and Table 5 shows the measurement results.

From Tables 2 and 3, Example 1 and Comparative Example 1 are examples in which the mass ratio of Ag powder and Pd powder is 70:30, and in Example 1, the resistor width is 0.5 mm x the resistor width is 50 mm. There is a small difference in temperature coefficient of resistance (TCR) between a resistor with a resistor width of 1 mm x a resistor width of 1 mm, and even a resistor with a resistor width of 1 mm x a resistor width of 1 mm has a temperature coefficient of resistance (TCR) ≦±. 500 [ppm/°C].
On the other hand, in Comparative Example 1 which does not contain silica, the temperature coefficient of resistance (TCR) of a resistor with a resistor width of 0.5 mm x a resistor width of 50 mm and a resistor with a resistor width of 1 mm x a resistor width of 1 mm are The difference is large, and the temperature coefficient of resistance (TCR) exceeds 500 [ppm/° C.] for a resistor with a resistor width of 1 mm x a resistor width of 1 mm.

From Tables 4 and 5, in Example 2, the difference in temperature coefficient of resistance (TCR) between the resistor with resistor width 0.5 mm x resistor width 50 mm and the resistor with resistor width 1 mm x resistor width 1 mm is small, and the resistance Even for a resistor having a body width of 1 mm x a resistor width of 1 mm, the temperature coefficient of resistance (TCR) is ≦±100 [ppm/° C.].
On the other hand, in Comparative Example 2, which does not contain silica, the temperature coefficient of resistance (TCR) of a resistor with a resistor width of 0.5 mm x a resistor width of 50 mm and a resistor with a resistor width of 1 mm x a resistor width of 1 mm are The difference is large, and the temperature coefficient of resistance (TCR) exceeds 100 [ppm/°C] for a resistor with a resistor width of 1 mm x a resistor width of 1 mm.

Further, in Example 3, the mass ratio of Ag powder to Pd powder was 44:56, and the amount of glass powder and silica powder was increased compared to Example 2. By increasing the amount of glass powder and silica powder, the area resistance value increases to approximately 10Ω, but the resistor has a resistor width of 0.5 mm x 50 mm and a resistor width of 1 mm x 1 mm. The difference in temperature coefficient of resistance (TCR) is small, and the temperature coefficient of resistance (TCR) is ≦±100 [ppm/° C.] even for a resistor having a resistor width of 1 mm×resistor width of 1 mm.

Furthermore, in Comparative Example 3 in which glass powder A in Example 2 was replaced with glass powder B having a softening point of 560°C, the temperature coefficient of resistance (TCR) exceeded 100 [ppm/°C] even though it contained silica powder. It ends up.

As can be seen from the above examples and comparative examples, according to the present invention, the temperature coefficient of resistance (TCR) can be adjusted to 0 [ppm/°C] even in resistors with small shapes and short distances between electrodes, which has been difficult in the past. I can do that.

Claims (4)

Contains noble metal powder, glass powder that does not substantially contain lead, and amorphous silica with a particle size of 50 nm or less,
The noble metal powder is a mixed powder containing 40 to 80% by mass of Ag powder and the balance consisting of Pd powder, or an alloy powder containing 40 to 80% by mass of Ag and the balance consisting of Pd and inevitable impurities,
The glass powder has a softening point of 650°C or more and 900°C or less,
A composition for a thick film resistor, comprising 1 to 100 parts by mass of the glass powder and 0.5 to 20 parts by mass of the amorphous silica, per 100 parts by mass of the noble metal powder. The composition for a thick film resistor according to claim 1, wherein the glass powder has a particle size distribution _D50 of 0.5 μm to 5 μm. A paste for thick film resistors comprising the composition for thick film resistors according to claim 1 or 2 and an organic vehicle in which a resin is dissolved in a solvent . A thick film resistor comprising a noble metal, glass substantially free of lead, and amorphous silica with a particle size of 50 nm or less,
The thick film resistor is a fired body, the noble metal contains 40 to 80% by mass of Ag, and the balance consists of Pd and inevitable impurities,
The glass has a softening point of 650°C or higher and 850°C or lower,
A thick film resistor characterized in that 1 to 100 parts by mass of the glass and 0.5 to 20 parts by mass of the amorphous silica are contained relative to 100 parts by mass of the noble metal.